Bronchopulmonary dysplasia (BPD) results from disrupted lung development after premature birth and results in life long pulmonary morbidity. Intrauterine and postnatal lung inflammation contribute to structural airway simplification and increased pulmonary vascular resistance, critical components of BPD. The Human Microbiome Project is designed to understand the interactions between microbial communities that inhabit a host and the host itself. Emerging data suggest that imbalances between components of commensal organisms in the gastrointestinal tract are associated with atopy, allergic rhinitis, or recurrent wheezing. These data prompt consideration of the role for gut microbiota-mediated lung inflammation as a trigger for BPD. In this single center project, limited polysomnography and echocardiography will be used to non- invasively and longitudinally assess airspace and pulmonary vascular development in premature newborns < 30 weeks' gestation who are at risk for developing BPD to test the hypothesis that signatures of the neonatal enteric microbiome are associated with BPD-related adverse pulmonary outcomes, including death, technology dependence, and need for bronchodilators or corticosteroids at 36 weeks and 1 year of age. Ongoing, parallel initiatives at Washington University that are characterizing the enteric microbiome of premature newborns will be leveraged to explore associations between this biomass and the development of BPD-related adverse pulmonary outcomes. The Specific Aims are: 1) utilize existing data to determine differences in the composition of the microbiota between groups of linked mothers and premature newborns with and without BPD, and 2) utilize existing data to determine differences in the metagenomic and/or transcriptional repertoire of the enteric microbiota between linked mothers and premature newborns with and without BPD. The metagenomic and transcriptional differences identified in Specific Aim II that are associated with adverse pulmonary outcomes will permit identification of factors that are amenable to early intervention and prevention of BPD, and furthermore, will inform selection of candidate gene networks that can be interrogated for the multicenter component of this proposal in which next generation sequencing will be used to identify the interactions between and among alleles of the infant and microbiota that are associated with BPD-related adverse pulmonary outcomes. RELEVANCE (See instructions): The proposed studies will evaluate whether bacteria in the intestinal tract of premature newborns play a role in the development of bronchopulmonary dysplasia, the most significant chronic lung problem of prematurity. Identifying the role that these bacteria play will permit early treatment in an effort to prevent the development of these lung problems. (End of Abstract)